Both ferrocene and carborane and derivatives thereof have been used as burning rate catalysts. Normal-butylferrocene and normal-hexylcarborane are typical ferrocene and carborane derivatives which have been used separately or in mixed catalyst systems for high burning rate propellants.
Various theories and proposed mechanisms for propellant burning rates have evolved from experimentation in the field of catalysis. A rate controlling step for propellant burning rates is based on the rate of decomposition of ammonium perchlorate. Burning rates have been measured for propellants wherein the particle size of ammonium perchlorate has varied. The burning rates of propellants increase as the particle size of the ammonium perchlorate is decreased. Smaller particle sizes facilitate the decomposition rate of ammonium perchlorate.
Very fine particle-sized ammonium perchlorate (e.g. of only a few microns average mean weight diameter particle size) and catalysts, generally which have been incorporated in the propellant compositon as liquid plasticizers, have helped to achieve high burning rates for propellant compositions. The use of the liquid-type catalysts has lead to other problems caused by catalyst-plasticizer migration into the liner-insulation system.
Desirable would be a catalyst which does not migrate after incorporation into propellant.
A highly effective catalyst to produce higher burning rates for a propellant composition is always desirable in that a small amount of catalyst can be used to change a propellant to yield the desired burning rates and ballistic properties.
A combination catalyst and oxidizer ingredient which can be used as a partial replacement for ammonium perchlorate without reducing the perchlorate ion content in the propellant would be even more highly desirable, especially if the catalyst-oxidizer ingredient is a solid ingredient and has excellent compatibility with the other propellant ingredients.
Therefore, an object of this invention is to provide a propellant ingredient which serves as a combined catalyst and oxidizer.
Another object of this invention is to provide a propellant ingredient which provides catalysis of the combustion process by at least two different reaction mechanisms.
A further object of this invention is to provide an oxidizer-catalyst ingredient which overcomes the problem of catalyst-plasticizer migration into the liner-insulation system.
Still a further object of this invention is to provide an oxidizer-catalyst ingredient which will permit the use of a lesser total amount of catalyst and ammonium perchlorate in a propellant formulation, and thereby permit the use of a larger quantity of binder, and/or fuel, and/or oxidizer in the formulation to yield a propellant of higher solids (metallic fuel, inorganic oxidizer) loading without adversely affecting the mechanical properties which is the situation which normally arises when the solids loading of a propellant is increased.